Microfluidic systems have been configured in various ways to move fluids through small channels. One configuration for channels where capillary forces dominate involves establishing a pressure differential between a point where the fluid is and a point where the fluid is to be moved. Other fluid pumps that address this problem of fluid flow utilize electrical, electrokinetic, or thermal forces to move fluids through microchannels. In instances where electrical driving forces are used, fluids may be moved through electrocapillary or electrowetting. In instances where electrokinetic forces are used, fluids may be moved through electrophoresis or electroosmosis. In addition, driving forces such as dielectrophoresis, electrohydrodynamic pumping, or magneto-hydrodynamic pumping are implemented by configuring electrodes and selecting and placing fluids within the microchannel in an appropriate manner.
For example, U.S. Pat. No. 5,632,876 utilizes electroosmosis and electrohydrodynamic principles, where wire electrodes are inserted into the walls of the channels at pre-selected intervals. As another example of fluid flow techniques, U.S. Pat. No. 6,949,176 uses capacitance forces to move fluid through a microchannel. In addition, the Knudsen pump, as described in U.S. Pat. No. 6,533,554 utilizes thermal transpiration for effecting gas flow.
However, there is a need for a fluid pump capable of efficient pumping of fluids, including gasses and liquids, which can have applications in small systems where capillary forces are not sufficient to create flow and Knudsen pumps are not workable.